Hydraulic braking systems for motor vehicles are known in many different variations. Such a braking system has at least one brake circuit in which at least one arrangement that conveys the pressure medium, a pump, in particular, is situated which is also designated as a return pump. In addition, at least one further arrangement for conveying the pressure medium may optionally be provided, especially a self-priming charge pump, which is connected via a suction line to a storage container for the pressure medium. The inlet and outlet of the pressure medium into the brake circuit is controlled, just as is the inlet and outlet of the pressure medium into the respective wheel brake cylinder, via cutoff devices for the inlet and/or the outlet and/or the passage of the pressure medium, particularly via valves. This is discussed in DE 195 46 682 A1, for example. In an electrohydraulic braking system, such as the one in DE 195 48 248 A1, one also finds this arrangement in principle, in which the pressure medium is supplied to valves or comes from valves by a pump via an interposed pressure reservoir. In this context, the pressure medium is introduced into the wheel brake cylinder or let out from it by opening and closing the inlet and outlet valves according to the braking command of the driver and/or the activating signals of a mediating logic, such as an antilock system, a traction control system or an electronic stability program.
With that, the described arrangement in principle applies in the same way, for instance, in a hydraulic braking system by a return pump having inlet and outlet valves or a charge pump having charge valves or switchover valves, and also as, for instance, in an electrohydraulic braking system by a turbine pump having inlet and outlet valves.
In the case of an unregulated pump actuation, in response to a pressure buildup or a pressure drop, in an emergency, there may be a noise development and/or vibrations which may have a disturbing effect in the passenger compartment. For this purpose, it may be provided that the pump is shut off after a pressure buildup or a pressure drop has taken place. However, in such a design approach it is a disadvantage that the final pressure created in the brake circuit, in this context, is not reproducible after the pump is shut off. The reason for this, among other things, is that the slowing down of the pump varies, based on different boundary conditions, such as the load, the friction, the rotary speed, the wear or the temperature that occur, and consequently supplies differently sized contributions to the final pressure. In addition, however, the switching performance of the valves present in the brake circuit is normally not clearly specifiable, since each valve has tolerances within certain limits based on the pressure present at it.